The manual provision and management of neighbor cells in conventional mobile networks is challenging and has become even more so as additional radio access technologies (RATs) have been developed and implemented. With respect to the Long Term Evolution (LTE) protocol, for example, neighbor relations must generally be maintained not only for other LTE cells to support intra-RAT cell reselection, but also for neighboring cells that operate in accordance with other radio access technologies to support inter-RAT cell reselection.
In order to facilitate the provisioning and management of neighbor cells, automatic neighbor relations (ANR) functionality has been developed. The ANR functionality generally resides in a base station, such as a Node B, an evolved node B (eNB) or the like. The ANR functionality of a Node B may maintain a listing of neighbor cells to facilitate handover or reselection thereto. For each neighbor cell, the neighbor list maintained by a Node B generally identifies the neighbor cells by means of a cell global identifier (CGI), an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) cell global identifier (ECGI), a physical cell identifier (PCI) or the like. A Node B may hold a black list of Node B cells that are not allowed for purposes of handover, reselection or the like; typically this black list relates to cells of a RAT that is different to that of the Node B in question. Thus, for example, a Node B associated with a UTRAN cell may hold a black list of Node B cells associated with GERAN or E-UTRAN cells.
In the context of a handover or cell reselection to a current cell, the Node B of the current cell may update the neighbor list with information regarding a cell that was previously serving a mobile terminal (a so-called “prior cell”). The information regarding the prior cell may be provided by the mobile terminal that was recently the subject of the handover or cell reselection since the mobile terminal was previously served by the prior cell and may therefore have neighbor information regarding the prior cell.
During cell relocation between cells of the same radio access technology, such as from one Universal Mobile Telecommunications System (UMTS) cell to another UMTS cell, the mobile terminal may be configured to log or store information regarding the prior cell or any other detected cells and to subsequently report the information regarding the prior cell or any other detected cells to the current cell at some subsequent point in time. However, in instances in which a mobile terminal reselects from a prior cell operating in accordance with one type of radio access technology to another cell operating in accordance with a different radio access technology, that is, an inter-RAT cell reselection, the mobile terminal may be configured to report the information regarding the prior cell to the current cell during or immediately following the reselection.
Examples of such inter-RAT cell reselection include reselection from a Global System for Mobile communications (GSM) Enhanced Data-rates for Global Evolution Radio Access Network (GERAN) or E-UTRAN cell to a UMTS cell. Prior to the reselection, the mobile terminal may have stored ANR information regarding the prior cell, such as the GERAN or EUTRAN cell, including, for example, frequency, PCI, CGI/cell ID, etc. During the cell reselection and registration process, the mobile terminal may provide an indication to the current cell, such as a UMTS cell, that signals that the mobile terminal has information, such as ANR information, regarding the prior cell. For example, the mobile terminal may transmit a Radio Resource Control (RRC) Connection Setup Complete message to the UMTS cell that includes a single bit that may be set to indicate that the mobile terminal has ANR information regarding the prior cell. The network, such as the UMTS cell, may then issue a message to the mobile terminal requesting the information, such as the ANR information, regarding the prior cell. For example, a UMTS cell may issue a User Equipment (UE) Information Request message to the mobile terminal soliciting the ANR information. The mobile terminal may then provide the information to the current cell, such as via a UE Information Response message, and the current cell may, in turn, update the neighbor list with the neighbor information regarding the prior cell.